How do I fix a broken electrical conduit that is attached to a concrete slab?

[MiamiCuse]

I have two rigid metal electrical conduits that came off the concrete slab along the exterior wall. One is next to the AC unit and one is next to the swimming pool filter and pump. The one next to the pool filter is an often wet area and the wires are exposed as seen here:

close up:

The conduit next to the AC unit has not broken off yet but will be soon, it is all corroded at the bottom:

close up:

Any suggestion how to fix that? Do I need to chip out the slab and make a hole to replace the conduit? or is there some sort of a mender to fix this kind of situation.

Thanks in advance,

MC

[buffalobill]

i think no electrical box is permitted at your point of damage, and your pictures show there is extensive damage. your electrician will evaluate the job and replace the full run from the nearby panel with appropriate gfci as required in your local ordinance. there may be hidden damage as well of wire corrosion that may reach toward the panel requiring a new breaker. he will determine the required limits for the path of the new conduit based on your local code.

general info at:

[MiamiCuse]

Thanks. But the nearby panel is 75 feet away on the other side of this concrete wall. Most of the runs are in rigid metal conduits either in the ceiling or inside walls, then it comes through the foundation out of the slab to service the AC or the pool pump. So this is really at the very end of the run where this exposed portion is damaged. The wires themselves seems fine, I don't think it is practically to run a new conduit from the garage all the way to this same location. There has to be some sort of repair kits?

MC

[John Grabowski]

Is that rigid conduit or EMT? I don't think that I have ever seen rigid corrode like that. Regardless, I am not aware of any quick fix repair kit. It is likely that water is inside the pipe and that the part under the slab is corroded as well. Is the conduit being used as a grounding conductor or is there a grounding conductor wire in the conduit? If the conduit is the grounding conductor, then it is probably not effective right now. I suggest that you cut back the conduit to where it is still good and install a junction/pull box and run new conduit using PVC.

[RBM]

I question the same thing. It looks like EMT to me. While EMT can be installed in concrete, it generally cannot be used as an underground conduit. If it is in wet ground under that slab, it may have all disintegrated, and would need to be replaced. The most important thing would be the system ground. Be sure that the conduits are not being used as the grounding conductor, and if they are, pull new ground conductors through them. Once your grounding is confirmed and adequate, you could possibly sleeve a length of PVC over the metal conduit to protect what's left of it

[dpb]

No repair kit but I don't believe there's a problem with an exterior weather-proof accessible box for the repair. (The key here is twofold

-- it's accessible, and it's not new but required repair work. I can't quote chapter/verse but believe code makes allowance for such circumstances.) But, it does need the conduit replaced from the point of good material to the other end through the slab to wherever it goes to make a good connection on an accessible location on the other side.

It looks like it would have been a lot easier to have done it when the new plastic that shows in the picture wasn't there from an access standpoint as you're going to have some good digging and hammering to get access, but what's done is done. You may find renting a small handheld jackhammer profitable depending on how much concrete is actually there and how good it still is.

I seriously doubt the conduit was/is the ground, but it is possible. Verify because you certainly don't have an effective ground if it was supposed to have been and you won't when you replace this section with platic which would be my suggestion to avoid the galvanic action of metal conduit in contact w/ concrete and standing water after every rain which is unavoidable given the geometry.

[MiamiCuse]

Good point with the ground I will double check. Not looking forward to breaking the concrete pad up.

Now the portion that is corroded but not yet broken off... is there a way to salvage that?

Can I spray something to slow the corrosion and wrap something around it? Guess not, it might break just by me messing with it.

Ouch...

MC

[RBM]

If it is steel tubing, which is what it looks like and you can chisel out concrete to a point where there is good metal, you could install a coupling and replace the bad section. If you do find good metal in the concrete, I'd suggest using a tubing connector and a threaded coupling, and changing to threaded galvanized pipe

[dpb]

...

Not knowing what is on the other side, I can't be certain, but I think the only correct repair is to replace the conduit from one accessible location to another on the inside of the wall. Whether it would be acceptable to simply add a section of conduit to or just below the present slab surface depends on whether the cable is underground/wet rated or not which is indeterminate from the pictures. Unless it is, it needs to be in the conduit all the way.

I think the only recourse here is to break out enough of a hole to be able to replace the section as needed. Once that's done, of course, the other thing you might consider is to run a (say) 2" outer conduit for the other to run inside and then re-pour around that leaving the inner conduit not in contact w/ the concrete. You would then need a weather seal on the outside to prevent rainwater, but if it's above the slab it wouldn't need to hold against standing water.

They original installation should never have poured concrete directly around what appears to be just EMT. And despite the other suggestion, you don't want a repair of non-electrical-rated conduit and plastic would be a far better choice.

[gfretwell]

You can probably just cut the wires 8" or so from the ground, set a box tight against the slab and continue with a good conduit from there with your splice in the box. As long as there is still a grounding path you should be OK. If they did not pull a grounding conductor you may be pulling the wires out adding a ground and pulling them back in. That is usually easier than trying to sneak a wire in. Pull a string in with the wires as you pull them out.

[dpb]

If do that need plastic box and seal and ensure have wet-rated cable. I'd still prefer the more extensive route but could perhaps get this to work ok. If not buried and wet cable, could, pull it for that section. Key thing I'm thinking of is that the conduit rusted off at the slab level is a water collector and even caulk doesn't hold permanently w/o to prevent water collecting in the old conduit eventually...

[Nate Nagel]

I'm thinking that this would be a good application for PVC, but it's a little late now...

nate

[gfretwell]

ALL underground conduits collect water and are required to have "wet location" rated conductors. The conduit is really just there for physical protection.

[aemeijers]

I hate doing any repairs twice. I'd be inclined to cut off and abandon the exisiting wiring in place, and find some better route for for the wire. The plumbing for A/C goes through the wall, not under it. Is there a basement where wires could be hidden in ceiling? Is there a soffit above, and an attic where wires could run?

aem sends...

[MiamiCuse]

No there is no basement. The way it is routed would be from the garage up to the attic and across the attic in rigid metal conduits then down the poured concrete wall and come out into the AC pad. I hate to chip out the concrete wall without knowing where the line really is. It is 1972 construction so it's not doing things according to today's code. I think the AC and pool filter / pump are the same line (I will check the breakers tomorrow), if it is I guess at least I can dig one up and reroute the other from there.

Thanks,

MC

[dpb]

But, there's a difference between an intact conduit and an open vertical end flush w/ a slab acting as a drain. I'm also wondering in the case if they buried EMT outside in concrete (as it looks like this was from the pictures), chances are the cable isn't what it should be as well.

I still don't much care for the idea of leaving the existing conduit on the slab level, even w/ the box sitting over it -- I'd go to the trouble of repairing the conduit run one way or another despite the extra effort. The idea of re-routing is a good one if feasible although I guess OP has kinda' put the kibosh on it...

[gfretwell]

This can't legally be "cable" in the first place. 680.22 requires the ground to be insulated 12ga or larger (for a pool pump). I suppose it could be MC cable with an insulated ground but pulling that through

1/2" EMT would be virtually inpossible.

[dpb]

...

...

Yes. I just meant "cable" in the generic sense "electrical conductors".

Looking at the picture OP posted was unable to tell what is actually there so was simply raising the caution flag. If the original installation used EMT outside through concrete as it appears I had/ have little confidence in anything else...